Comment # 2 on bug 907682 from Wolfgang Bauer

(In reply to ill lume from comment #0)
> After installing plasma-session5, kwin5 auto installed with it, however the
> old kwin was not auto-removed and is still present

I strongly disagree that kwin5 and kwin should conflict.
They can coexist nicely, no need to artificially break that.
And I do want to have both installed.

Plasma 5 should use kwin5 by default even if the KDE4 version is installed as
well, it does here at least.

> and is the version that
> runs by default at bootup instead of kwin5. I think this is a bug because
> the newer kwin should run by default.

Yes, Plasma5 should run kwin5 by default, and as mentioned already it does so
here.

And why do you think the KDE4 version is running?
What does "ps ux|grep kwin" say? (run inside a Plasma5 session of course)